Spectroscopic imaging combines digital imaging and molecular spectroscopy techniques, which can include Raman scattering, fluorescence, photoluminescence, ultraviolet, visible and infrared absorption spectroscopies. When applied to the chemical analysis of materials, spectroscopic imaging is commonly referred to as chemical imaging. Instruments for performing spectroscopic (i.e., chemical) imaging typically comprise image gathering optics, focal plane array imaging detectors and imaging spectrometers.
In general, the sample size determines the choice of image gathering optic. For example, a microscope is typically employed for the analysis of sub micron to millimeter spatial dimension samples. For larger objects, in the range of millimeter to meter dimensions, macro lens optics are appropriate. For samples located within relatively inaccessible environments, flexible fiberscopes or rigid borescopes can be employed. For very large scale objects, such as planetary objects, telescopes are appropriate image gathering optics.
Regardless of the type of optical equipment, a first step in any spectroscopic investigation is defining a suitable wavelength for illuminating the sample. The step of defining a suitable wavelength for illuminating the sample becomes even more important when simultaneous multiple images of the sample are sought. Conventional methods suggest illuminating a sample with a first wavelength (e.g., NIR or VIS) to obtain a first image, followed by illuminating the sample with a second wavelength to obtain a second image (e.g., Raman or dispersive Raman). Consequently, the conventional process is time consuming and is not suited for simultaneous imaging of the sample. There is a need for an apparatus and method for determining illumination parameters of a sample a priori of illuminating the sample.
The current disclosure addresses the need described above. In one embodiment, the disclosure relates to a method for obtaining a chemical image of a biological sample by providing a biological sample labeled with a Fluorophore; irradiating the sample with photons having wavelength within the illumination wavelength range; obtaining a spectral image of the sample; and generating a chemical image from the spectral image. The chemical image may define at least two spectral images of the sample obtained simultaneously. The spectral images can include a Raman image and a fluorescent image.
In another embodiment, an apparatus for obtaining a spectral image of a biological sample comprising means for determining a range of illumination wavelengths, the illumination wavelength interacting with the sample to simultaneously provide a first and a second spectra of the sample; a photon source for directing photons with a wavelength within the range to the sample, the illuminating photons interacting with the sample to produce interacted photons; a tunable filter for receiving interacted photons and forming a spectral image of the sample.
In still another embodiment, the disclosure relates to a system for obtaining multiple spectra of a biological sample. The system can include a processor programmed with instructions to determine illumination parameters of the sample as a function of the emission bandwidth of said sample; an illumination source for directing photons having a wavelength within the illumination parameters of the sample, the illuminating photons interacting with the sample to provide interacted photons; and a tunable filter for receiving the interacted photons from the sample and providing at least a first and a second spectra of the sample.